605A - presumably that's at the load end of the cable. Thinking of worst case (cables cold when measured) and potentially warm before a fault, then we need to adjust - in the lack of any more information I'll use the 80% rule (probably not entirely right as the pyro could be running hotter than 70-degrees, but will do to be going on with) - so let's say 484A.

That's still off the appendix 3 charts - so <<0.1s disconnection time. Really we should look up the manufacturer's energy let-through, but if the adiabatic works for 0.1s, then we're safe anyway.

Presuming (again looking for the worst case) that the pyro is PVC sheathed or exposed to touch, k=115